Applicant claims, under 35 U.S.C. xc2xa7 119, the benefit of priority of the filing date of Jul. 30, 2001 of a German patent application, copy attached, Serial Number 101 37 014.8, filed on the aforementioned date, the entire contents of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a position measuring system, having a graduation support, a detector arrangement, adjusting device for setting a scanning distance, and a coupling element.
2. Discussion of Related Art
A position measuring system basically includes a graduation support and a detector arrangement for scanning the graduation on the graduation support. Here, the detector arrangement generates position-dependent scanning signals. The quality of these scanning signals is a function of the distance between the graduation support and the detector arrangement. In connection with measuring steps required these days, a graduation period of the graduation of a few micrometers is required. The smaller the graduation period, the more accurately must a preset scanning distance, which is a function of the scanning principles, be adjusted.
So-called modularly constructed position measuring systems are becoming more and more successful for reasons of cost and space-saving installation. With a modularly constructed position measuring system, the position measuring system does not have its own seating, or guidance, for the graduation support, therefore the relation between the detector arrangement and the graduation support is not preset and must be adjusted by an adjusting device in the course of the installation on the objects to be measured. Modularly constructed angle measuring systems without an associated seating are also called modular encoders.
A position measuring system in the form of an angle-measuring system is known from U.S. Pat. No. 5,057,684, the entire contents of which are incorporated herein by reference. An adjusting device can be displaced by a hoop-shaped actuating member in the direction of the scanning distance, i.e. axially from a mounting position into an operating position, for setting the scanning distance. This displacement takes place in a recess of the holder of the detector arrangement. In actuality the holder and the adjusting device axially displaceable therein are mostly made of plastic. It has been found that for manufacturing reasons the adjusting device has a relatively large play in the recess of the holder. Because of this play, the radial relation between the graduation support and the detector arrangement remains undefined during mounting. The radial distance of the graduation from the detector arrangement has a tolerance as a function of the play. With the continuing increase of miniaturization, the radial width of the graduation, as well as of the detector element, is relatively small. In many cases there are several graduation tracks arranged next to each other on the graduation support. For scanning, the detector arrangement has detector elements which are also arranged next to each other. Too great a radial play between the adjusting device and the holder can result in the required relation between the graduation and the detector element not being achieved.
It is therefore an object of the present invention to disclose a position measuring system wherein the adjusting device better assures the correct position relation between the graduation and the detector arrangement.
This object is attained by a position measuring system that includes a graduation support having a first detent and a detector arrangement on a holder for scanning the graduation support at a preset scanning distance. An adjusting device that sets the preset scanning distance, the adjusting device is displaceable relative to the holder along a first direction from a mounting position to an operating position. The adjusting device includes a second detent which, in the mounting position, acts together with the first detent of said graduation support acting in the first direction, and the first and second detents are out of engagement at the operating position and a receiver which, at the mounting position, maintains the graduation support oriented perpendicularly with respect to the first direction, and the receiver is removed from the graduation support by being displaced in the first direction. A coupling element that couples the adjusting device free of play with the holder at least in a second direction perpendicular with respect to the first direction.
An advantage of this position measuring system in accordance with the present invention lies in that the correct position relation between the graduation and the detector element is assured without any great technical manufacturing outlay. The guidance of the adjusting device is free of play, at least in the required direction which sets the distance between the graduation and the detector arrangement (perpendicularly in relation to the scanning distance).
Exemplary embodiments of the present invention will be explained in greater detail by the drawings.